This invention relates to multiple curtain, open front refrigerated display cases.
The rising cost of energy has recently caused concerned review of the economics and energy usage of open front refrigerated display cases. These have replaced a substantial market share of the glass door reach-ins or chest-type cabinets because of the several advantages including potentially higher sales capacity, greater convenience, and more effective display of product. While the relative energy loss from open front cases is greater than from the closed door-type during shopping hours, the difference is not as large as might be anticipated due to the fact that the door-type are constantly opened and closed. However, relative energy loss during the closed store hours is significant. Actually, this factor was recognized years ago and as a result, night covers as set forth in U.S. Pat. Nos. 3,465,536 and 3,496,732 were devised in efforts to cover open front display cabinets during such hours. These night covers constituted removable, heavily insulated structures which are sealed tightly to the cabinet to prevent leaks from between them. The insulation was provided to prevent condensation of the structure tending to interfere with the system and even freeze the cover in place. Any air leaks between the structure and the display case, even tiny ones, were found to cause significant frost accumulation at that area, to interfere functionally with the equipment, potentially freeze the cover in place, and generally present a frost problem. These covers unfortunately were large, bulky and cumbersome, requiring special daytime storage, evening retrieval, and protection against damage or distortion which would prevent the necessary tight fitting characteristics. These factors together proved such a problem that the covers were never really accepted as practical.
Another more recent type of night cover is that set forth in U.S. Pat. No. 3,241,899. This unit is retractable, being mounted directly on the display case itself. Such covers are presently marketed. When used to cover dairy case structures wherein the temperatures are above freezing, these covers do cause a considerable power savings during non-shopping hours. Therefore, the assignee herein, a manufacturer of diary-type cases recommends the usage of such covers for these cases.
In comparison with the dairy-type display cases with temperatures above the freezing point, however, the frozen food open front display cases which are below freezing temperatures have significantly greater energy loss. And, sub-zero , open front display cases for ice cream and the like have the greatest energy loss. These frozen food and ice cream open front display cases are today almost totally of the multiple curtain-type for maximum efficiency. Yet, the roll-up curtain-type cover has really not been particularly advantageous for these high energy cases. Firstly, there is a problem as to where to place it. The manufacturer of these curtains presently advises placement of the curtain over the multiple of air curtains, i.e. encompassing the guard curtains too. Although the manufacturer recommends this, experimentation by the assignee herein, a manufacturer of display cases, has shown that placement of the curtain in this fashion on low temperature cases does not result in any significant savings of energy. If the curtain were to be placed immediately over the inner refrigerated air curtain, i.e. and not over the other curtains of air, frost formation and freezing would occur on and about the curtain. This is totally unacceptable to the store manager. Thus, the assignee does not presently recommend use of the curtain to purchasers of low temperature (i.e. frozen food and ice cream) open front multiple curtain display cases.
As is known, until recently the energy loss from multiple curtain open front refrigerated display cases has simply been tolerated. Presently, with rapidly rising energy costs and a general desire to conserve energy, the sale of these open front display cases is significantly declining, being replaced by sales of the older door-type, even in spite of their significant sales disadvantages.